The control of odor in animal litter has been a continuing problem. Suggested solutions include the use of bacteriostats such as: halogenated aromatic hydrocarbons (U.S. Pat. No. 4,494,482, Arnold, issued Jan. 22, 1985); soluble salts of transition metals of Group Ib or Group IIb of the periodic table of elements, especially zinc, which are taught as both bacteriostats and urease inhibitors (U.S. Pat. No. 4,494,481, Rodriguez et al., issued Jan. 22, 1985 and U.S. Pat. No. 4,736,706, Lang, issued Apr. 12, 1988); boron containing compounds which are claimed to be urease inhibitors (U.S. Pat. Nos. 4,949,672 and 5,176,108, Ratcliff et al. and Jenkins et al., issued Aug. 21, 1990 and Jan. 5, 1993 respectively); sodium bisulfite complexes (U.S. Pat. No. 5,267,531, Appel et al., issued Dec. 7, 1993); and sodium or potassium bicarbonate (U.S. Pat. Nos. 5,303,676 and 5,421,291, Lawson and Lawson et al., issued Apr. 19, 1994 and Jun. 6, 1995 respectively). Other approaches to controlling odor include the use of absorbents for odor such as cyclodextrin and polycarboxylate polymers (U.S. Pat. Nos. 4,727,824; 4,844,010; 4,881,490; and 4,883,021, Ducharme et al., issued Mar. 1, 1988; Jul. 4, 1989; Nov. 21, 1989; and Nov. 28, 1989 respectively).
Still another approach of "covering up" the bad odor involves using encapsulated perfiumes (U.S. Pat. No. 4,407,231, Colbom et al. issued Oct. 4, 1983). Thus, many commercial cat litter products contain a fragrance to mask the malodor and to provide a freshness impression. Many of these fragrances are developed with human aesthetic preference in mind, apparently without consideration of the effect to the animal Thus, many perfumes used in commercial cat litter compositions contain significant amounts of ingredients that are repulsive to cats. On the other hand, commercially available products which claim control of animal behavior, such as cat repellent and cat attractant products, contain only the purported active ingredients without consideration to human aesthetics.
Many types of materials are used as animal litter. Clay and various cellulosic materials are commonly used, as disclosed in the above patents and additional disclosures of materials that can be used are found in U.S. Pat. Nos.: 5,064,407, Peiffer, issued Nov. 12, 1991; U.S. Pat. No. 5,100,600, Keller et al., issued Mar. 31, 1992; U.S. Pat. No. 5,207,389, Hall et al., issued May 4, 1993; U.S. Pat. No. 5,209,186, Dewing, issued May 11, 1993; and U.S. Pat. No. 5.229,348, Ivie, issued Jul. 20, 1993. Preferred animal litter materials are those that "clump" to permit ready removal of the material that has been contacted by, e.g., urine and/or feces. such as U.S. Pats. Re. No. 33,983, Hughes, issued Jul. 7, 1992 and U.S. Pat. No. 5,193,489, Hardin, issued Mar. 16, 1993. All of the above patents are incorporated herein by reference.